The aim of this project is to identify mechanisms of action of new drugs. This information will facilitate a) optimal design of clinical trials, b) integration of the agents into combination therapy regimens, c) development of approaches that will selectively protect host tissues, and d) development of desirable modifications of current agents. Primary mouse tumor systems used will be sarcoma 180, leukemia L1210 and neuroblastoma model. Cultured human cell lines of neuroblastomas and brain tumors are also available for some experiments. Incorporation of radiolabeled precursors will be followed in vivo and in vitro: thymidine and uridine into nucleotides and nucleic acids; phenylalanine into the proteins; acetate into lipids; and these precursors and aminosugars into membranes. The measurements of the integrity of nucleic acids will be made by neutral and alkaline sucrose density-gradient ultracentrifugation. Cell-free systems of ribosomes and synthetic messenger will be used to study protein synthesis in vitro. Intracellular uptake, distribution and metabolism of drugs will be studied by high-pressure liquid chromatography, fluorometry, and spectrophotometry. Changes in the function and integrity of the cell membrane will be assayed by transport of metabolites and binding of, and agglutination by concanavalin A. Microtubule protein will be measured by colchicine-binding assay using DEAE, and competition by other drugs determined. Transport of drugs will be studied in cell suspensions, using a spin through isotonic sucrose to separate the cells from drug-containing medium. Pharmacological disposition will be studied when it is helpful to an understanding of mechanisms of action. The methodology will include fluorometry, spectrophotometry, column, thin-layer and high pressure liquid chromatography, and extraction procedures.